As semiconductor devices have become more highly integrated, concave capacitors have been implemented to overcome some of the structural limitations of pillar type capacitors or one-cylindrical stack (OCS) type capacitors. A concave capacitor can be formed using a hole in a molding layer, and forming a lower electrode, a dielectric layer and an upper electrode in the hole. Forming the hole to have a great aspect ratio may be advantageous in increasing capacitance of the capacitor, but may create problems due to the limitation in the patterning process.
Another method to overcome some of the limitations of the patterning process, while also forming the hole to have a greater aspect ratio, includes forming a lower molding layer on a substrate, and forming a lower hole that passes through the lower molding layer. A sacrificial layer can fill the lower hole and an upper molding layer can be formed on the lower molding layer and the sacrificial layer. An upper hole exposing the sacrificial layer through the upper molding layer can be formed. The sacrificial layer may be removed to connect the upper hole to the lower hole. Due to errors in the patterning process, however, the upper hole may slightly deviate from the lower hole and in a contact area of the upper hole and the lower hole, the upper hole may have a different size than the lower hole. Moreover, a sidewall of the upper and lower hole may have a sharp slope and create an under-cut in the contact area. The sidewall having a sharp slope may prevent the forming of the lower electrode close to the dielectric layer.